Instant messaging (IM) has grown from simple messaging in the 1960's, bulletin board systems of the 1980's, and messaging applications of the 1990's, into the field of unified communications, which provides real-time communications services such as unified messaging (integrated email, voicemail, fax, instant messaging, and presence information), telephony, and video conferencing. Enabling many of these IM features are a number of messaging and presence protocols, such as Instant Messaging and Presence Service (IMPS), Extensible Messaging and Presence Protocol (XMPP), and Session Initiation Protocol (SIP) with its extension SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE), to name a few.
XMPP, also known as “Jabber”, is the current Internet Engineering Task Force (IETF) standard for instant messaging and presence. In addition to server-mediated instant messaging, XMPP has been augmented with a signaling mechanism (called “Jingle”) to establish unmediated peer-to-peer sessions, such as voice or video sessions. Such peer-to-peer sessions are used to supplement the normal course of instant messaging, e.g., by carrying on a voice conversation in parallel with a text session. The connection that is already established by virtue of XMPP presence can be exploited for peer-to-peer session establishment.